Telephone system



Nov. 16 1926.

1,606,794 K. S. JOHNSON TELEPHONE SYSTEM Filed June 4. 1923 fi L j'c LMQ E III \JC fim mm Patented Nov. 16, 1926.

UNITED sTATEs PATENT OFFICE.

KENNETH S. JOHNSON, OF JERSEY CITY, NEVT JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Application filed June 1-, 1923.

This invention relates in general to tele phone systems and more particularly to intercommunicating systems of the code ringing. common battery type.

The object of this invention is, in general, to provide a simple, inexpensive intercommunicating system suitable for use where only a few stations are required, or where the number of calls is comparatively small.

Heretofore in intercomnmnication systems of the three wire type a separate retardation coil and source of current were required for each station and in those systems using a single retardation coil and source of current tour wires were necessary.

In accordance with this invention, only three conductors and a single retardation coil and source of current are used to perform all the signaling and talking operations.

The drawing shows schematically the wiring of a three-station system embodying the invention, but the provision of any desired number of stations is contemplated. The system comprises three line wires or conductors 1, 2, 3, one or" which conductors lea 3, is a common return for both the signaling and talking circuits. Line wire 3 is con nected with line wire 2 through a source of current 10 which may be a battery of dry cells. Line wire 2 is connected to line wire 1 through retardation coil 9, one terminal of which may be connected at the common junction point 11 of the line wire 2 and the terminal of the battery 10. The common return conductor 3 may be a water or gas pipe or any other suitable ground, thus reducing to two the number of wires which has to be installed.

All stations of the system are similar and are so connected in parallel with each other across the line wires 1, 2 and 3 that ringing is accomplished using line wires 1, 2 and 3, while voice current flows through line wires 1 and 3. The retardation coil 9 has a high impedance to alternating current and hence prevents the voice current generated by a transmitter from being shunted through the battery 10.

At station A line wire 1 is normally connected through switch arm and its lower contact, to ringing switch 4, and its upper contact, through buzzer or hell 8 to line wire 2. The upper contact of switch arm 5 is connected through receiver 6 and transmit- Serial No. 643,169.

ter 7, to line Wire or ground 3. The other stations, B and C, are connected similarly to station A.

Assume that any one of the stations such as A desires to call any other station such as B. The calling party presses the ringing key 1.. thus closing a circuit from the positive side of batterylO, through line wire 3, lower contact of ringingkey 4 switchhook 5., line wire 1, switchhook 5 upper contact of ringing key 41,, bell or buzzer 8 line wire 2 to negative side of battery 10. In like manner a circuit is closed through the hell or buzzer of every station except the calling station, and also through retardation coil 9. The bells of the stations will therefore, ring simultaneously since the re sistance of the retardation coil is sufiiciently high to prevent its interfering with the ringing operation. The called station will be known by the particular code signal transmitted.

When the receivers are removed from the hooks, there is established a series talking circuit from transmitter 7,, receiver 6,, conductor 1, receiver 6 transmitter 7 and conductor 3 back to transmitter 7,. Current from battery 10, flows through transmitter 7 in series with its receiver 6 and also through the parallel path comprising transmitter 7,, and its receiver 6 the combined current returning to the battery by way of retardation coil 9. The sets at the two stations are thus supplied with battery and the voice current which may be thought of as generated by the transmitters, passes, for example, from transmitter 7,, receiver 6,, conductor 1, receiver 6 transmitter 7 and conductor 3 back to transmitter 7 This current is prevented from flowing through battery 10 by the high impedance to alternating current of retardation coil 9, as is well understood in the art.

What is claimed is:

1. A communicating system comprising a plurality of stations each equipped with talking and signaling apparatus, three conductors connecting said stations, an impedance connected across the first and the second of said conductors, a source of current connected across the second and the third of said conductors, said impedance and source of current being common to all the stations on said system, switching means at each station operative to connect the talkconductors one of which serves as the common return for the other two, a single retardation impedance connected in bridge of one of the conductors and said common return, a source of current connected in bridge of the other conductor and said common return, a plurality of stations each comprising signaling and talking apparatus similarly connected to said conductors, a sw1tch- -hook and a key at each station, a circuit branch at each station normally closed through said switchhook, key and signaling apparatus, connections whereby said key in its calling position opens said circuit branch at the calling station and PTOJQCiLS signal current over said system to the called station,

" and connections whereby said switchhook at each station when in talking position also opens said circuit branch at that station and connects said talking equipment to the system. i

- 1 3. A communicating system comprising a plurality of stationsfeach equipped with talking and signaling apparatus, three con- 7 ductors connecting said stations, one of said conductors serving as the common return for the other two conductors, a source of current common-to said stations connected between thecommon return and one of said other conductors, the signal apparatus at-each station being connected, in the idle condition of the station, across the said other two conductors, means at each station for connecting the'talking' apparatus thereat between the opposite one of said other conductors from that to which said source of current is connected and said common return, and means at each station operative in calling to dis connect the signal apparatus thereat'from across said two conductors and to project current from said source to the called station over a circuit comprising said two last mentioned conductors.

at. in a telephone system, a alurality of stations, three conductors interconnecting the same, a battery and a retardation coil connected in series across two of the conductors and common to said stations, telephone instruments connected across said two conductors, the third conductor being connected to the junction point of said coil and battery and interconnecting said stations, 9. manual signaling switchrat each station, a signal at each station connected to said third conductor and to one 01"- said talking conductors through the normal contacts of the associated manual switch and switchhook, said manual switch at alternate contacts connee-ting one pole of the battery to said last mentioned talking conductor.

In witness whereof, I hereunto subscribe my name this 29th day of May A. D., 1923.

KENNETH s. JonNsoNi 

